Often depicted in movies and video games are cowboy-ish characters with a thick accent calling each other their "partner". I realize it's a similar thing to "dude", but its origin is unknown to me.
I have not read ALL primary sources, but I have not seen this use of the word "partner" in an actual text - other than to describe an actual partner. It appears to be a convention from movies at the least, and perhaps dime novels as well (but that is outside my research area).
Do we know that it's an accurate depiction, or is it a made-up movie convention?